Duplex turbine shroud

Abstract

A gas turbine engine shroud includes a row of different first and second shroud segments alternating circumferentially therearound. The first segments have a first pattern of first cooling holes extending therethrough. The second segments have a second pattern of second cooling holes extending therethrough. The corresponding patterns have different collective flowrate capabilities.

1. A gas turbine engine apparatus comprising:
 an annular combustor having a row of fuel injectors; 
 an annular turbine nozzle following said combustor and having a row of vane doublets with axial splitlines therebetween; 
 a row of turbine blades following said nozzle; 
 a duplex turbine shroud surrounding said blades, and comprising a row of different first and second shroud segments alternating circumferentially around said blades; 
 said first segments having a first pattern of first cooling holes clocked with said fuel injectors for receiving hot combustion streaks therefrom over said first cooling holes; and 
 said second segments having a second pattern of second cooling holes clocked offset with said injectors for receiving cold combustion streaks from the spaces therebetween over said second cooling holes, wherein said second cooling holes have smaller diameters than said first cooling holes. 
 
     
     
       2. An apparatus according to  claim 1  wherein each of said first and second shroud segments comprises:
 a panel having opposite front and back surfaces, with forward and aft hooks extending from said back surface to define a pocket therebetween; and 
 said first and second cooling holes extend through said panels from said pockets to said front surfaces, with said second cooling holes having a reduced collective flowrate capability than said first cooling holes. 
 
     
     
       3. An apparatus according to  claim 2  wherein:
 said first cooling holes are inclined under said forward hook in said first segments; and 
 said second cooling holes are inclined under said forward hook in said second segments and have a smaller collective flowrate capability than said first cooling holes. 
 
     
     
       4. An apparatus according to  claim 3  wherein said first and second patterns further comprise a plurality of third cooling holes extending through said panels from said pockets to said front surfaces aft of said first and second cooling holes. 
     
     
       5. An apparatus according to  claim 4  wherein said second pattern has fewer second cooling holes than said first pattern has first cooling holes. 
     
     
       6. An apparatus according to  claim 4  wherein said third cooling holes have the same diameter and position in said first and second patterns. 
     
     
       7. An apparatus according to  claim 6  wherein:
 each of said first and second segments includes respective corners bridging the leading edge of said panels and lateral edges thereof along said forward hooks; and 
 said corners include identical ones of said third cooling holes terminating near said leading edge and laterally bounding said first and second cooling holes in said first and second segments. 
 
     
     
       8. An apparatus according to  claim 7  wherein said first and second segments and said first and second patterns are substantially identical except for said different first and second cooling holes therein. 
     
     
       9. An apparatus according to  claim 8  wherein:
 said first shroud segments are clocked with said nozzle splitlines for receiving said hot combustion streaks over said first cooling holes; 
 said second shroud segments are clocked between said vanes in each doublet for receiving said cold combustion streaks over said second cooling holes; and 
 said second cooling holes are smaller in diameter than said first cooling holes. 
 
     
     
       10. A duplex turbine shroud comprising:
 a row of different first and second shroud segments alternating circumferentially; 
 said first segment having a first pattern of first cooling holes extending therethrough; and 
 said second segment having a second pattern of second cooling holes extending therethrough, wherein said second cooling holes are different in size than said first cooling holes. 
 
     
     
       11. A shroud according to  claim 10  wherein each of the said first and second segments comprises:
 a panel having opposite front and back surfaces, with forward and aft hooks extending from said back surface to define a pocket therebetween; and 
 said first and second cooling holes extend through said panels from said pockets to said front surfaces with different collective flowrate capabilities. 
 
     
     
       12. A shroud according to  claim 11  wherein:
 said first cooling holes are inclined under said forward hook in said first segment; and 
 said second cooling holes are inclined under said forward hook in said second segment and have a different collective flowrate capability than said first cooling holes. 
 
     
     
       13. A shroud according to  claim 12  wherein said first and second patterns further comprise a plurality of third cooling holes extending through said panels from said pockets to said front surfaces aft of said first and second cooling holes. 
     
     
       14. A shroud according to  claim 13  wherein said second pattern is different than said first pattern. 
     
     
       15. A shroud according to  claim 14  wherein said second pattern has fewer second cooling holes than said first pattern has first cooling holes. 
     
     
       16. A shroud according to  claim 15  wherein said first and second cooling holes have the same diameters. 
     
     
       17. A shroud according to  claim 13  wherein said third cooling holes in said second segment match said third cooling holes in said first segment. 
     
     
       18. A shroud according to  claim 17  wherein said third cooling holes have the same diameter and position in said first and second patterns. 
     
     
       19. A shroud according to  claim 13  wherein:
 each of said first and second segments includes respective corners bridging the leading edge of said panels and lateral edges thereof along said forward hooks; and 
 said corners include identical ones of said third cooling holes terminating near said leading edge and laterally bounding said first and second cooling holes in said first and second segments. 
 
     
     
       20. A shroud according to  claim 10  wherein said second cooling holes have smaller diameters than said first cooling holes. 
     
     
       21. The shroud of  claim 10  in combination with an upstream turbine nozzle and annular combustor having a row of fuel injectors, and said first shroud segments are clocked with said injectors for receiving hot combustion streaks therefrom over said first cooling holes thereof. 
     
     
       22. A combination according to  claim 21  wherein said second shroud segments are clocked offset with said injectors for receiving cold combustion streaks from the spaces therebetween over said second cooling holes of said second segments. 
     
     
       23. A combination according to  claim 22  wherein:
 said turbine nozzle includes a row of vane doublets having axial splitlines therebetween; 
 said first shroud segments are clocked with said nozzle splitlines for receiving said hot combustion streaks over said first cooling holes; 
 said second shroud segments are clocked between said vanes in each doublet for receiving said cold combustion streaks over said second cooling holes; and 
 said second cooling holes are smaller in diameter than said first cooling holes.